The present invention relates to valve lifters for use with internal combustion engines. More particularly, to a hydraulically switchable lifter-based device, which accomplishes cylinder deactivation in push-rod engines, and most particularly to such a device having a pressurized oil groove or grooves for routing air away from the switching oil supply.
Cylinder deactivation is the deactivation of the intake and/or exhaust valves of a cylinder or cylinders during at least a portion of the combustion process. Cylinder deactivation is a proven method, by which fuel economy can be improved. With fewer cylinders performing combustion, fuel efficiency is increased and the amount of pollutants emitted from the engine is reduced. A known method of providing cylinder deactivation in a push rod engine is by using a deactivation mechanism in the hydraulic valve lifter.
Preferably, for optimum packaging, the deactivation mechanism in a push rod engine is contained within the general envelope of a conventional hydraulic valve lifter. Such a device disclosed in commonly assigned U.S. Pat. No. 6,513,470 and incorporated herein by reference. In such a device, hydraulically operated latch pins are used to decouple concentrically disposed members of the deactivation roller hydraulic valve lifter (DRHVL). When in the decoupled mode, reciprocating motion imparted on the DRHVL via the rotating camshaft is isolated from the associated push rod and rocker arm deactivating the associated engine valve and its related cylinder.
This pumping motion, however, causes air bubbles to form in the oil surrounding the DRHVL and further causes the bubbles to be directed toward the oil supply used to switch the deactivation device from its coupled to decoupled mode. Since the decoupling event must be precisely timed to occur on demand, the presence of compressible air bubbles in the switching oil negatively impact the precision at which the DRHVL can be decoupled or decoupled.
Therefore, what is needed in the art is a device, which will shield air bubbles from entering the switching oil supply for the DRHVL. Moreover, what is needed in the art is a device that redirects the air bubbles away from the switching oil supply for the DRHVL.
A deactivation hydraulic valve lifter which includes an elongate lifter body having a substantially cylindrical outer surface and an inner wall, the inner wall defining at least one annular pin chamber therein. The outer surface defining at least one annular groove in fluid communication with a high-pressure oil gallery of an engine, the lifter body having a lower end configured for engaging a cam of the engine.